"We have a President who has proposed again and again to shut down this tank factory, the only one we have, over a budget gimmick," Mr. Ryan told a crowd inside the Veterans Memorial Civic & Convention Center.
"If we keep showing that the only thing we want to do is gut our military, that projects weakness abroad, our adversaries are so much more willing to test us, our allies are so much less willing to trust us. We need peace through strength," he said.
Mr. Ryan addressed a crowd of 1,680 during the first day of three days of campaign visits by him and ticket leader Mitt Romney. Mr. Ryan speaks today in Cincinnati and then meets Mr. Romney in Dayton. On Wednesday, Mr. Romney will rally supporters in Dayton, Columbus, Cleveland, and Toledo.
President Obama will campaign Wednesday in Bowling Green and Kent, Ohio.
The Pentagon has said it has enough Abrams tanks and wants to halt production for several years as it wrestles with deep cuts in military spending over the next decade.
The government-owned plant that employs 800 people is operated by General Dynamics Corp. The company has estimated the cost of shutting down the plant and then restarting it at $1.6 billion, while keeping it open with minimal production over four years would cost $1.4 billion, the Associated Press has reported.
The Army puts the price of pausing production at around $400 million.
The Obama for Ohio campaign fired back that Mr. Ryan voted for the automatic spending cuts that could trigger large cuts in the nation's defense budget.
“The only thing ensuring that these cuts will become reality is Mitt Romney and Congressman Ryan’s opposition to asking for a penny more from millionaires and billionaires," said campaign spokesman Jessica Kershaw. She accused Mr. Romney of planning to cut deductions for mortgage interest, children, and charitable contributions to provide millionaires with tax cuts. So far, Mr. Romney hasn't said how he would pay for tax cuts.
Mr. Ryan turned part of his time over to taking questions from the audience, and he used a slide show with graphs to address the nation's deficit and debt problems.
Asked by one questioner to explain Mr. Romney's "47-percent" remark, Mr. Ryan said - to the crowd's approval, "We want an opportunity society, not a welfare state."
He said the Romney administration's measure of success would be not how many people are on food stamps "but how many we get off of them."
Mr. Ryan said President Obama's statement in an interview on the Spanish-language Univision network last week that he can't change Washington from the inside was revealing.
"That is why you send presidents to Washington - to fix what's broken in Washington. Since he's admitted he can't change Washington, we need to change presidents," Mr. Ryan said.
Ohio is getting well over its share of presidential campaigning attention because the state's 18 electoral votes are up for grabs, and because they are considered essential for Mr. Romney to win the 270 electoral votes needed for victory, and highly desirable for Mr. Obama as well.
Allen County, the home of Lima, went 60.5 percent for Republican John McCain in 2008 over Mr. Obama, who carried the state with 51.5 percent of the vote.
Outside the convention center, about 30 supporters of President Obama rallied across Market Street from the hundreds of Romney-Ryan supporters who waited to enter the civic center.
Several carried signs that said, "Mitt Romney: writing off the middle class" and "My job is not to worry about those people," references to Mr. Romney's recently disclosed remark at a videotaped fund-raising event that 47 percent of the country is dependent on government and is not likely to support him for President.
"Without Obama standing up for the auto industry the UAW as we know it would not exist today," said Larry Donaldson, past president of UAW Local 2147. An employee of the Lima tank plant, operated as a public-private entity, Mr. Donaldson said Mr. Obama is not trying to cut the military excessively, whereas he thinks Mr. Romney is proposing too much of a military build-up.
"I think what he's got in mind is war with Iran," Mr. Donaldson said.
Romney supporters said they think Mr. Romney and Mr. Ryan have the right ideas to revive the nation's economy.
Hannah Shreffler, 22, a senior in political science at Ohio Northern University in Ada supporting Mr. Romney, pointed to what she said was a small turnout among the Obama supporters.
"I think that speaks well for our cause, for our campaign and our candidate, that we're lining up around the block and an area that has some high industry, some high union rates is having a somewhat small demonstration," Ms. Shreffler said. "Maybe the support for Obama has gone down in the last four years. There's obviously some diehards that still stand by him but a lot of people have seen his record, and are starting to change."
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